The present invention relates to apparatus for heating a vehicle seat. More particularly, the present invention can be applied in motor vehicles, for heating electrically heatable seats for occupants in the vehicle. The present invention also relates to a method for heating such a vehicle seat.
For reasons of both comfort and safety, electrically heatable seats are used in modern vehicles. Both the driver""s seat and the other seats in the vehicle can be arranged such that they can be heated by means of special heating elements in the form of electrically conducting wires which are placed in the shape of a heating coil in each seat. Such a heating element is normally placed in the cushion and the back-rest of each seat when manufacturing the seat. The heating element is also connected to a current feeding unit which delivers current. In this manner, the heating element can be heated to a suitable temperature.
A problem of previously known heating elements is caused by the desire for each seat to have a carefully adjusted temperature on its surface, i.e., on that surface which is in contact with the person sitting in the seat. For this purpose, the temperature of the heating element can be controlled by means of a temperature detector which is arranged in close proximity to the heating element, and which is connected to a central control unit. Using the temperature detector and the control unit, the current temperature can be detected. The control unit also comprises current feeding circuits which, for example, can be based on transistor or relay technology, for feeding a current to the heating element. In this way, the central control unit is arranged to feed a certain current to the heating element until a certain desired value for the temperature is reached. The setting of this desired value can be accomplished by means of fixed resistances or by means of an adjustable potentiometer, which is adjusted by a person travelling in the vehicle.
Using the above-described control method, current can be delivered to the heating element until the central control unit indicates that the desired value has been reached. When this happens, the control unit will interrupt feeding of the current. This causes the heating element to gradually cool down. When the heating element has cooled so that its temperature again falls below the desired value, current feeding to the heating element will be resumed. In this way, the temperature control will continue for as long as the system is operative.
Although previously known systems normally provide for reliable heating and temperature control for a vehicle seat, they may imply certain disadvantages. One such disadvantage relates to the fact that previously known systems demand unique temperature switches, a unique wiring and unique electronics units for all different variations of switches (for example On/Off, Off/Low/High, Off/Low/Medium, etc.) which may occur in different seat types and vehicle types. This results in extensive and complicated wiring arrangements between the control unit of the heating element and the various switches. Furthermore, the previously known systems require that the control unit of the heating element comprise particular hardware for different configurations of switches.
Another disadvantage related to previously known systems relates to the fact that the heating element is normally mounted in the vehicle seat during manufacturing thereof. In this regard, the heating element is adapted to a particular xe2x80x9cstandard seat,xe2x80x9d i.e., a seat type of a predetermined kind having a particular design, upholstery, etc. Consequently, the vehicle seat comprises a heating element for the purpose of heating the surface of the seat to a particular desired temperature. However, during assembly of the complete vehicle the manufacturer might choose to equip the vehicle seat in question with, for example, a completely different upholstery, for example a considerably thicker upholstery than that of the xe2x80x9cstandardxe2x80x9d vehicle seat, i.e., an upholstery which differs from that for which the temperature control was originally intended. The temperature value which is detected by the temperature sensor will reach the set desired value when the heating element has reached the desired temperature, but since an abnormally thick upholstery is mounted on the seat, the temperature on the surface of the seat will be too low. This situation thus causes an undesired deviation during the temperature control.
One object of the present invention is thus to provide for improved heating of a seat in a vehicle, where the above-mentioned drawbacks have been eliminated.
In accordance with the present invention, apparatus has been devised for heating a vehicle seat comprising a heating element for heating the vehicle seat, a temperature sensor for detecting the temperature created by the heating element, a control unit connected to the heating element, the control unit comprising current feeding means for feeding a current to the heating element if the temperature measured by the temperature sensor is below a predetermined desired temperature, a communication member for receiving information from an external source, an external operating unit separated from the control unit, at least one functional member connected to the external operating unit, the external operating unit including programmed logic means for generating information based on the state of the at least one functional member, and programmed function means for transmitting the information, and a transmission channel for transmitting the information from the external operating unit to the control unit, whereby the control unit can be operated by means of the information. Preferably, the programmed logic means includes data relating to the design of the vehicle seat, and wherein the information comprises information relating to the predetermined desired temperature.
In accordance with one embodiment of the apparatus of the present invention, the communication member includes information transfer means for transferring additional information to the external operating unit, and the external operating unit includes additional information receiving means for receiving the additional information from the communication member and indication means for indicating receipt of the additional information and the condition of the at least one functional member. In a preferred embodiment, the additional information comprises information relating to the condition of the heating element and/or the control unit.
In accordance with one embodiment of the apparatus of the present invention, the additional information comprises a start pulse for initiating a periodical sequence during which the additional information is transferred.
In accordance with another embodiment of the apparatus of the present invention, the control unit comprises an oscillation circuit for transferring pulses having a predetermined periodicity, the pulses corresponding to the information.
In accordance with another embodiment of the apparatus of the present invention, the control unit has a limited validity time period, whereby after the limited validity time period has elapsed following receipt of the information by the control unit, the current feeding means reduces the current fed to the heating element to a predetermined value.
In accordance with another embodiment of the apparatus of the present invention, the control unit includes logic means, and the current feeding means includes switch means, the logic means, the switch means and the communication member comprising an integrated circuit. Preferably, the logic means, the switch means and/or the communication member are disposed on a common silicon chip.
In accordance with the present invention, a vehicle has also been devised including the above apparatus in which the external operating unit comprises a single silicon chip including all of the logic functions for programming the generation of the information.
In accordance with another aspect of the present invention, a method has been devised for heating a vehicle seat including a heating element for heating the vehicle seat and a control unit connected to the heating element for feeding a current to the heating element, the method comprising detecting the temperature created by the heating element, feeding the current to the heating element if the detected temperature is less than a predetermined desired temperature, and transferring information to the control unit from an external operating unit including generating the information based upon the state of at least one functional member utilizing programmed logic and transmitting the information to the control unit by means of programmed functions. In a preferred embodiment, the method includes generating the information based on data relating to the design of the vehicle seat, and the information relates to the predetermined desired temperature, and the method includes transferring the information in the form of a plurality of pulses corresponding to the predetermined desired temperature. Preferably, the method includes decreasing the current to the heating element after a limited validity time period elapses.
In accordance with one embodiment of the method of the present invention, the method includes transferring additional information relating to the condition of the heating element from the control unit to the exterior operating unit, and including indicating receipt of the additional information and the condition of the at least one functional unit.
In accordance with another embodiment of the method of the present invention, the method includes transferring additional information relating to errors in the control unit and components connected to the control unit from the control unit to the exterior operating unit.
In accordance with another embodiment of the method of the present invention, the method includes transferring the additional information from the control unit to the exterior operating unit in the form of at least one pulse and in accordance with a periodical sequence controlled by the control unit. Preferably, the method includes indicating each period of the periodical sequence with a start pulse transferred from the control unit.
In accordance with another embodiment of the method of the present invention, each period of the periodical sequence has a duration corresponding to a predetermined first time interval, and the method includes transferring the additional information from the control unit to the exterior operating unit during a second predetermined time interval, and the transfer of the information from the external operating unit to the control unit takes place during a third predetermined time interval. In a preferred embodiment, the method includes controlling the second and third predetermined time intervals by the control unit.
In accordance with another embodiment of the method of the present invention, the method includes controlling the second and third predetermined time intervals by the first predetermined time interval, and calculating the second and third predetermined time intervals in the exterior operating unit.
In accordance with another embodiment of the method of the present invention, the second predetermined time interval comprises from about 10% to 30% of the first predetermined time interval and the third predetermined time interval comprises from about 70% to 90% of the first predetermined time interval.
In accordance with another embodiment of the method of the present invention, the method includes interrupting the feeding of the current to the heating element if the plurality of pulses is outside of a predetermined range.
In accordance with another embodiment of the method of the present invention, the method includes setting a device including a flip-flop, a switch, a register or a counter to zero if the plurality of pulses is outside of a predetermined range.
In accordance with another embodiment of the method of the present invention, the method includes transmitting the information serially through a transmission cable between the control unit and the exterior operating unit.
The apparatus according to the present invention is intended for heating a vehicle seat which comprises a heating element which is connected to a control unit. The control unit comprises current feeding means for feeding a current through the heating element for the heating thereof. Furthermore, a temperature sensor is connected to the control unit for detection of the temperature created by the heating element, and wherein the control unit is adapted for feeding the current if the measured temperature is lower than a predetermined desired temperature. The control unit also comprises a communication unit for receiving information from an external operating unit by means of a transmission channel for the transfer of the information. In accordance with the present invention, the operating unit is connected to at least one functional unit for operating the control unit by means of the transferred information. In this regard, the operating unit comprises programmed logic functions for generating the information, at least depending on the state of the functional unit, and programmed functions for transmitting the information to the communication unit.
The operating unit used in accordance with the present invention allows for a simplified device and a simplified method for heating a vehicle seat. By means of the present invention, an economically advantageous solution is provided due to the fact that the operating unit can be manufactured from relatively low-cost, standard electronic components in a highly compact design, and can thereafter be programmed in order to provide the necessary functions, for example, for the vehicle type or vehicle seat in question.
The apparatus according to the present invention preferably operates entirely standing alone with respect to a central computer unit or the like in a motor vehicle, and consequently does not require any particular adaption of such a computer unit. The apparatus and the method according to the present invention is based on a modular concept in which a high degree of flexibility is obtained by means of a few standardized and uncomplicated electronic components.
According to one advantageous embodiment of the present invention, the information comprises information related to the desired temperature, wherein the operating unit is arranged to generate the information based on data stored in the operating unit related to the design of the vehicle seat.
The apparatus according to the present invention provides a very high degree of reliability, due to the fact that most of the components forming part of the invention can be integrated on a few integrated circuits.